How Do Radar Detectors Work?

No, they are not cop detectors.

byChris Rosales|
Accessories photo
Chris Rosales


We may earn revenue from the products available on this page and participate in affiliate programs. Learn more ›

Radar detectors aren’t exactly a key component in the average driver’s toolbox. That said, no, it isn’t a “cop detector” like some folks are led to believe. It is a tool that works in specific ways and doesn’t work in others, and the information it provides needs to be interpreted using the knowledge I will impart to you.

They’re also definitely not a free pass to speed, though that is the implication. 

The truth is that it’s an awareness tool that you need to use along with visual observation and some basic knowledge of how radar detectors work, which actually isn’t too complicated. It’s all based on an incredibly basic technology: radio.

Radar Detectors Detect Radio Waves

Radar is just a form of radio wave, which is used to locate objects in space. It is a complicated technology based on simple physics, but the gist of it is that radio waves reflect off objects. A receiver can send out waves and calculate the time it takes for waves to return, which gives a fairly accurate reading of an object’s distance, size, and shape. Though the world in radar looks much different to the world in the visual spectrum.

Chris Rosales

For the purpose of radar detectors, they detect specific bands of radio waves. The bands that detectors work in are usually X band, K band, and Ka-band, which are historically the frequencies used by police radar guns. These days, most states have switched to Ka guns and laser-based guns. The radar guns emit radio waves to get an accurate reading of the speed of cars on the highway, which is a valuable tool for speed enforcement.

A radar detector is essentially purpose-built to detect police radar guns. Thus, their ability to detect specific bands of radar prevents too much interference and white noise from clouding its ability to detect. But it does not simply detect a police car or any signals a police car emits. It detects radar waves in those bands.

Why A Radar Detector Is Necessary

You also don’t need to be a wanton speeder to need a radar detector, as it is a useful tool that can prevent costly fines for minor speeding, and give you an early warning of the presence of an intrepid state trooper. More importantly, it can save you the time and hassle of getting pulled over, and potentially going to court. 

Chris Rosales

Now, we aren’t saying to brazenly break the law. The point of a radar detector is solely for police detection. It is up to you how much risk you want to take with speed and the lives of other road users.

There are some downsides to radar detectors. They are totally legal to use in passenger vehicles in most states, save for Iowa, Virginia, and Washington D.C. Even in states where detectors are legal, law enforcement may try to harass you for obstructing the windshield or other peripheral violations to try and get you to remove the detector. Generally speaking, a quality low-profile rearview mirror mount will circumvent this.

Chris Rosales

Also, some states including the ones that outlaw detectors have radar detector detectors. This is where the market gets murky because some radar detectors actually emit their own detectable waves that police can use to enforce usage. High-end detectors from companies like Escort and Uniden have countermeasures against this. 

Can You Install A Radar Detector At Home?

Yes, very easily. Most consumer-grade detectors are designed to be installed extremely easily. All you will need is a pair of hands, a dedicated radar detector mount (which usually comes with it), and some time. 

Some of Our Favorites

The Drive and its partners may earn a commission if you purchase a product through one of our links. Read more.

More from The Drive